HA agent has an error : cmd addnode failed for primary node: Internal AAM Error – agent could not start. : Unknown HA error error
Got the error on a vSphere 4.1 host. I have three hosts in the cluster and the other two are working fine. After doing some investigation I edited the \etc\hosts file on the vSphere hosts and found it had the wrong IP address for one of the hosts in the cluster. Fixed that and issued a reconfigure HA command to the host resolved the issue!